(1) Field of the Invention
The present invention relates to the field of aircraft, and in particular rotorcraft, and it relates more particularly to on-board equipment for monitoring the operation of a power plant fitted to such an aircraft. The present invention relates more specifically to drainage circuits for a flow of at least one liquid coming from a power plant fitted to a rotorcraft, and leading to discharge to the outside environment.
(2) Description of Related Art
Rotorcraft are fitted with one or more power plants for driving rotation of at least one rotor, or indeed for driving at least one accessory of the rotorcraft. The power plant is generally installed in a compartment of the rotorcraft airframe. Such a compartment is commonly arranged in the top portion of the rotorcraft fuselage, close to the main rotor of the rotorcraft that serves to provide the rotorcraft with lift and possibly also propulsion.
Under such conditions, there arises the general problem of monitoring and maintaining the power plant. It is desirable to facilitate such monitoring as much as possible, including when performed by an inexperienced operator. Rotorcraft are commonly subjected to regular maintenance inspections that are complex and performed by a qualified operator, but it is also appropriate to allow a rotorcraft pilot to act quickly and easily at a stopover to monitor the operation of the power plant.
Power plants comprise a variety of members, such as for example a main engine for propelling the rotorcraft, cooling apparatus, a main gearbox, or any other member that incorporates and/or that is fitted with a circuit and/or a tank of liquid that is needed in its operation.
The leaktightness of members making use of a liquid, and analogously of any circuits associated with conveying the liquid, is not always perfect. This can lead to a leak of liquid that it is desirable to discharge to the environment outside the rotorcraft, in particular to avoid a potentially flammable liquid stagnating close to the power plant. It is also appropriate to monitor for the presence of any such liquid leak that is excessive, and this monitoring should be done regularly and it should be easy to do, in particular it should be possible for a rotorcraft pilot to do during a stopover or for any operator without special qualifications to do, and indeed it is also appropriate to generate a warning message in the event of any such excessive leak of liquid being detected.
It is conventional for rotorcraft to be fitted with a drainage circuit relying on natural flow of one or more liquids leaking from the power plant to the outside of the rotorcraft. Such a drainage circuit has one or more liquid flow ducts, including at least one downstream duct that leads to the environment outside the rotorcraft. Such a downstream duct may discharge to the outside environment not only the leakage liquid coming from at least one member of the power plant, but also runoff water that might be retained in the environment close to the power plant.
For example, a duct is interposed between the outside environment of the rotorcraft and a bottom wall of a compartment housing the power plant. All of the liquids that might be present in the compartment are collected and conveyed by the duct in order to be discharged to the outside. Said liquids are likely to be functional liquids that have leaked from members of the power plant, or else runoff water that has accumulated in the compartment as mentioned above.
Also by way of example, a drainage circuit comprises one or more individual drainage circuits, each having at least an upstream duct and a downstream duct. The upstream duct is in hydraulic communication at its upstream opening with a potential source of leakage liquid coming from the power plant, and at its downstream opening with the downstream duct. The liquid is conveyed by natural flow via the upstream duct and then via the downstream duct in order to be discharged to the outside.
In a first variant of an individual drainage circuit, a said upstream duct and a said downstream duct form an overall duct connecting an exclusive source of leakage liquid with the outside environment. The drainage circuit has a plurality of respective overall ducts allocated to draining various liquids coming from respective members of the power plant. The drainage circuit also has a specific duct for discharging runoff water, which duct is disposed between the outside environment and a bottom wall of a compartment housing the power plant.
In a second variant, the individual drainage circuit comprises an upstream duct leading to a downstream duct that is common to all of a plurality of individual circuits used for discharging liquids coming from potential sources of leakage liquid. The downstream duct is commonly formed by a downstream duct that includes a said duct for discharging runoff water.
Monitoring for a potential leak of a liquid can be performed using a device incorporated in the drainage circuit. Such a device may include a member for collecting a leakage liquid conveyed by the drainage circuit and associated with warning means for issuing a warning when a significant quantity of liquid has been collected in excess of a predefined threshold corresponding to a nominal flow that is acceptable for the leakage liquid.
For example, according to document U.S. Pat. No. 3,623,053 (General Electric) a drainage duct for a leakage liquid in an aircraft is fitted with a warning device relating to a flow of a significant quantity of liquid in the duct that is considered as being excessive. The liquid may come from a fuel tank, or indeed from any functional member of the aircraft.
The device described in document U.S. Pat. No. 3,623,053 includes a liquid collector cup housed inside the duct. In its bottom, the cup has a liquid escape opening allowing the liquid to escape at an acceptable liquid flow rate. For a predetermined quantity of liquid collected inside the cup, means for detecting the predetermined quantity of liquid serve to generate a warning signal. The detector means use a probe formed by a tube for detecting the presence of liquid retained in the bottom of the receptacle, said probe being in communication with means for generating a warning signal.
Such a device for issuing a warning of an excessive flow of liquid in the duct needs to be improved.
By way of example, improvements need to be provided concerning the ways in which the device might be integrated in any drainage circuit and concerning the use of the device for any source of leakage liquid. The physicochemical characteristics of the liquid, and in particular its viscosity, and the flow rate of the liquid inside the drainage circuit are likely to differ significantly from one source to another.
By way of example, it is also desirable for the device to be suitable for being installed on any aircraft, taking account of the origin of the liquid, and at any location suitable for a drainage circuit operating by a natural flow of the liquid. The architecture of the drainage circuit may be of any kind and may be very varied from one aircraft to another.
Also by way of example it is appropriate to ensure that the information that might be generated by the warning means is reliable and to improve its pertinence, while also enabling it to be used by personnel having no specific qualification in aircraft maintenance, e.g. the pilot or personnel assisting the pilot.
Account should also be taken of the device being installed safely in the drainage circuit.
Account should also be taken of the competitivity of the device, meaning that costs should be kept down concerning the fabrication of the device, its incorporation and installation in a drainage circuit, its use, and its maintenance.
Technological background remote from the invention also includes the following documents: DE 295 16 718, JP 54 160041, and DE 100 47 586.